Field
The embodiment of the present invention relates to a memory system.
Description of the Related Art
As memory systems capable of storing mass data for use, variable resistance memories including cell arrays easily formable in three dimensions, such as a ReRAM (Resistance RAM) and an ion memory, have received attention.
In these memory systems, as one of methods for raising the density of information storage, there is a method of fine pattering a cell array. The use of this method, however, requires higher technologies and causes a problem about cost rises. Another method includes multi-valuing a cell. This method is an effective method because it causes almost no cost rise. In the case of this method, however, physical quantity levels of a cell become unstable. Therefore, unprecedented different ideas are required for writing data to a cell, storing data by a cell and reading data from a cell.